Devices of various types are commercially available for testing and evaluating batteries, starters, alternators in vehicle systems, as well as for testing battery chargers. Often, however, a technician will independently test the battery, alternator and starter only to find that each of these components tests good even though the vehicle owner is experiencing difficulties in operation of the vehicle. Such difficulty may be caused, for example, by high impedance in the system that limits available cranking current when the system is under load. High impedance may be the result of contributing factors, such as poor connections at various circuit locations, circuit elements that are not individually accessible for connection to the tester, or a combination of individual faults. A cable itself may have inherent impedance that is detrimental to the system. Use of conventional DC ohmmeters with conventional testing methods are unable to obtain readings having fine enough resolution to detect such cable impedance.
A need exists for a tester that can provide a continuous reading or display of impedance at various circuit points of the system so that the technician can readily and immediately observe the change in impedance as the tested circuit points are changed. Such provision would also be of significant benefit for real time display of the effects on impedance by changes in loading conditions of the system. A need also exists for a testing method capable of high resolution impedance detection.
A shortcoming of conventional testers is the difficulty in connecting test leads to remote circuit points in a vehicle. In a large truck, for example, system circuit elements near the front of the vehicle may be readily accessible while connection of the test leads to other test points is inconvenient or impossible with conventional test leads. A further need thus exists for an ability to readily gain access to any test point in the electrical system.